1. Field of the Invention
The present invention relates to flat cables for high-frequency signal transmission applications and more particularly, to a high-frequency digital A/V cable, which provides enhanced EMI protection.
2. Description of the Related Art
In recent years, audio and video application designs have been well developed. Nowadays, many audio and video products, such as VCD, DVD, digital versatile disc, high-definition digital TV, videophone, video conference system and the like are now intensively used in our daily life. When compared to conventional techniques, these new system architectures utilize digital technology to process voice and image data. Subject to different requirements for application in different fields, different standards are established, modified and updated to improve digital signal transmission (without compression) in speed and quality so that people can enjoy better quality audio and video quality. HDMI, DVI and DisplayPort are digital video interface standards designed to maximize the visual quality of digital display devices. A DisplayPort, DVI or HDMI connector is connectable to an adapter, set-top box, DVD player, PC, TV game machine, synthesized amplifier or digital audio equipment for long distance application to transmit audio video signals stably at a high speed, satisfying consumers' requirements.
A DisplayPort, DVI or HDMI connector can be used with a round or flat cable. A cable for this purpose comprises a plurality of high-frequency signal lines and a plurality of low-frequency signal lines. During signal transmission, transmission interference may occur between the high-frequency signal lines and the low-frequency signal lines, resulting in transmission instability and interference with surrounding electronic devices. In actual practice, the conventional high-frequency digital cables have the following drawbacks:
1. The internal grounding wire can simply transfer noises from the signals to the earth, they cannot eliminate electromagnetic interference.
2. The insulation layers that surround the metal core wires of the high-frequency signal lines and low-frequency signal lines cannot protect the respective metal core wires against interference of external noises.
Therefore, it is desirable to provide a high-frequency digital A/V cable that eliminates the aforesaid drawbacks.